Transactions with Affiliates and Related Parties - Summary of Transactions (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Affiliated entities
Related party transactions
Cash and due from banks	$ 41,874	$ 39,408	$ 24
Other assets	23,872	2,765	1,080
Noninterest-bearing demand deposits	(456)	(2,990)	(41,137)
Other liabilities		(18,709)
Interest income from affiliates			70
Interest expense to affiliates			(7)
Noninterest income from affiliates	4,908	7,757	8,615
Noninterest expense to affiliates	(47)	(39)	(54)
Bank of the West (BOW) \| Commitments to purchase foreign currencies
Related party transactions
Notional amounts		74	4,108
BancWest Corporation (BWC) \| Expense reimbursements
Related party transactions
Reimbursements received	$ 21,400	$ 24,800	$ 0

Amount of cash and due from banks arising from transactions with related parties.

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- Definition

Total aggregate amount of all noninterest expense incurred from transactions with related party.

+ References

No definition available.

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- Definition

The total amount of noninterest income earned from transactions with related party.

+ References

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- Definition

For an unclassified balance sheet, amount of other assets arising from transactions with related parties.

+ References

No definition available.

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- Definition

For an unclassified balance sheet, amount of other liabilities arising from transactions with related parties.

+ References

No definition available.

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- Definition

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column B

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- Definition

Amount of interest expense incurred on a debt or other obligation to related party.

+ References

No definition available.

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- Definition

Amount of interest income earned from interest-bearing assets owed to the entity by related party.

+ References

No definition available.

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- Definition

Amount of deposits held by the entity for a related party (entity, shareholder, employee).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(k))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

Reflects the sum of all other revenue and income realized from sales and other transactions (excluding transactions that are eliminated in consolidated or combined financial statements) with related party during the period.

+ References

No definition available.

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